Aberration of social behavior and gut microbiota induced by cross-fostering implicating the gut-brain axis.

The gut microbiota and neurological development of neonatal mice are susceptible to environmental factors that may lead to altered behavior into adulthood. However, the role that changed gut microbiota and neurodevelopment early in life play in this needs to be clarified. In this study, by modeling early-life environmental changes by cross-fostering BALB/c mice, we revealed the effects of the environment during the critical period of postnatal development on adult social behavior and their relationship with the gut microbiota and the nervous system. The neural projections exist between the ascending colon and oxytocin neurons in the paraventricular nuclei (PVN), peripheral oxytocin levels and PVN neuron numbers decreased after cross-fostering, and sex-specific alteration in gut microbiota and its metabolites may be involved in social impairments and immune imbalances brought by cross-fostering via the gut-brain axis. Our findings also suggest that social cognitive impairment may result from a combination of PVN oxytocinergic neurons, gut microbiota, and metabolites.

Oxytocin neurons in the paraventricular nucleus and fear empathy among male mice.

BACKGROUND: Recent studies have identified empathy deficit as a core impairment and diagnostic criterion for people with autism spectrum disorders; however, the improvement of empathy focuses primarily on behavioural interventions without the target regulation. We sought to compare brain regions associated with empathy-like behaviours of fear and pain, and to explore the role of the oxytocin-oxytocin receptor system in fear empathy. METHODS: We used C57BL mice to establish 2 models of fear empathy and pain empathy. We employed immunofluorescence histochemical techniques to observe the expression of c-Fos throughout the entire brain and subsequently quantified the number of c-Fos-positive cells in different brain regions. Furthermore, we employed chemogenetic technology to selectively manipulate these neurons in Oxt-Cre-/+ mice to identify the role of oxytocin in this process. RESULTS: The regions activated by fear empathy were the anterior cingulate cortex, basolateral amygdala, nucleus accumbens, paraventricular nucleus (PVN), lateral habenula, and ventral and dorsal hippocampus. The regions activated by pain empathy were the anterior cingulate cortex, basolateral amygdala, nucleus accumbens, and lateral habenula. We found that increasing the activity of oxytocin neurons in the PVN region enhanced the response to fear empathy. This enhancement may be mediated through oxytocin receptors. LIMITATIONS: This study included only male animals, which restricts the broader interpretation of the findings. Further investigations on circuit function need to be conducted. CONCLUSION: The brain regions implicated in the regulation of fear and pain empathy exhibit distinctions; the activity of PVN neurons was positively correlated with empathic behaviour in mice. These findings highlight the role of the PVN oxytocin pathway in regulating fear empathy and suggest the importance of oxytocin signalling in mediating empathetic responses.

A ratiometric fluorescent probe revealing the abnormality of acetylated tau by visualizing polarity in Alzheimer's disease.

Abnormal neuronal polarity leads to early deficits in Alzheimer's disease (AD) by affecting the function of axons. Precise and rapid evaluation of polarity changes is very important for the early prevention and diagnosis of AD. However, due to the limitations of existing detection methods, the mechanism related to how neuronal polarity changes in AD is unclear. Herein, we reported a ratiometric fluorescent probe characterized by neutral molecule to disclose the polarity changes in nerve cells and the brain of APP/PS1 mice. Cy7-K showed a sensitive and selective ratiometric fluorescence response to polarity. Remarkably, unlike conventional intramolecular charge transfer fluorescent probes, the fluorescence quantum yield of Cy7-K in highly polar solvents is higher than that in low polar solvents due to the transition of neutral quinones to aromatic zwitterions. Using the ratiometric fluorescence imaging, we found that beta-amyloid protein (Aß) inhibits the expression of histone deacetylase 6, thereby increasing the amount of acetylated Tau protein (AC-Tau) and ultimately enhancing cell polarity. There was a high correlation between polarity and AC-Tau. Furthermore, Cy7-K penetrated the blood-brain barrier to image the polarity of different brain regions and confirmed that APP/PS1 mice had higher polarity than Wild-type mice. The probe Cy7-K will be a promising tool for assessing the progression of AD development by monitoring polarity.

High salt diet exacerbates cognitive deficits and neurovascular abnormalities in APP/PS1 mice and induces AD-like changes in wild-type mice.

High salt diet (HSD) is a risk factor of hypertension and cardiovascular disease. Although clinical data do not clearly indicate the relationship between HSD and the prevalence of Alzheimer's disease (AD), animal experiments have shown that HSD can cause hyperphosphorylation of tau protein and cognition impairment. However, whether HSD can accelerate the progression of AD by damaging the function of neurovascular unit (NVU) in the brain is unclear. Here, we fed APP/PS1 mice (an AD model) or wild-type mice with HSD and found that the chronic HSD feeding increased the activity of enzymes related to tau phosphorylation, which led to tau hyperphosphorylation in the brain. HSD also aggravated the deposition of Aß42 in hippocampus and cortex in the APP/PS1 mice but not in the wild-type mice. Simultaneously, HSD caused the microglia proliferation, low expression of Aqp-4, and high expression of CD31 in the wild-type mice, which were accompanied with the loss of pericytes (PCs) and increase in blood brain barrier (BBB) permeability. As a result, wild-type mice fed with HSD performed poorly in Morris Water Maze and object recognition test. In the APP/PS1 mice, HSD feeding for 8 months worsen the cognition and accompanied the loss of PCs, the activation of glia, the increase in BBB permeability, and the acceleration of calcification in the brain. Our data suggested that HSD feeding induced the AD-like pathology in wild-type mice and aggravated the development of AD-like pathology in APP/PS1 mice, which implicated the tau hyperphosphorylation and NVU dysfunction.

Rotenone aggravates PD-like pathology in A53T mutant human α-synuclein transgenic mice in an age-dependent manner.

Multiple factors such as genes, environment, and age are involved in developing Parkinson's disease (PD) pathology. However, how various factors interact to cause PD remains unclear. Here, 3-month and 9-month-old hα-syn+⁣/- mice were treated with low-dose rotenone for 2 months to explore the mechanisms that underline the environment-gene-age interaction in the occurrence of PD. We have examined the behavior of mice and the PD-like pathologies of the brain and gut. The present results showed that impairments of the motor function and olfactory function were more serious in old hα-syn+/- mice with rotenone than that in young mice. The dopaminergic neuron loss in the SNc is more in old hα-syn+/- mice with rotenone than in young mice. Expression of hα-syn+/- is increased in the SNc of hα-syn+/- mice following rotenone treatment for 2 months. Furthermore, the number of activated microglia cells increased in SNc and accompanied the high expression of inflammatory cytokines, namely, TNF-α and IL-18 in the midbrain of old hα-syn+/- mice treated with rotenone. Meanwhile, we found that after treatment with rotenone, hα-syn positive particles deposited in the intestinal wall, intestinal microflora, and T lymphocyte subtypes of Peyer's patches changed, and intestinal mucosal permeability increased. Moreover, these phenomena were age-dependent. These findings suggested that rotenone aggravated the PD-like pathologies and affected the brain and gut of human α-syn+/- transgenic mice in an age-dependent manner.

Simultaneous Sensing of H2S and ATP with a Two-Photon Fluorescent Probe in Alzheimer's Disease: toward Understanding Why H2S Regulates Glutamate-Induced ATP Dysregulation.

Energy deprivation and reduced levels of hydrogen sulfide (H2S) in the brain is closely associated with Alzheimer's disease (AD). However, there is currently no fluorescent probe for precise exploration of both H2S and adenosine triphosphate (ATP) to directly demonstrate their relationship and their dynamic pattern changes. Herein, we developed a two-photon fluorescent probe, named AD-3, to simultaneously image endogenous H2S and ATP from two emission channels of fluorescent signals in live rat brains with AD. The probe achieved excellent selectivity and good detection linearity for H2S in the 0-100 µM concentration range and ATP in the 2-5 mM concentration range, respectively, with a detection limit of 0.19 µM for H2S and 0.01 mM for ATP. Fluorescence imaging in live cells reveals that such probe could successfully apply for simultaneous imaging and accurate quantification of H2S and ATP in neuronal cells. Further using real-time quantitative polymerase chain reaction and Western blots, we confirmed that H2S regulates ATP synthesis by acting on cytochrome C, cytochrome oxidase subunit 3 of complex IV, and protein 6 of complex I in the mitochondrial respiratory chain. Subsequently, we constructed a high-throughput screening platform based on AD-3 probe to rapidly screen the potential anti-AD drugs to control glutamate-stimulated oxidative stress associated with abnormal H2S and ATP levels. Significantly, AD-3 probe was found capable of imaging of H2S and ATP in APP/PS1 mice, and the concentration of H2S and ATP in the AD mouse brain was found to be lower than that in wild-type mice.

Synergistic effects of hIAPP and Aß1-42 impaired the olfactory function associated with the decline of adult neurogenesis in SVZ.

According to many in the field，the prevalence of Alzheimer's disease (AD) in type II diabetes (T2DM) populations is considerably higher than that in the normal population. Human islet amyloid polypeptide (hIAPP) is considered to be a common risk factor for T2DM and AD. Preliminary observations around T2DM animal model show that the decrease of adult neural stem cells (NSCs) in the subventricular zone (SVZ) is accompanied by olfactory dysfunction. Furthermore, impaired olfactory function could serve as to an early predictor of neurodegeneration，which is associated with cognitive impairment. However, the synergistic effects between hIAPP and amyloid-beta (Aß) 1-42 in the brain and the neurodegeneration remains to be further clarified. In this study, olfactory capacity, synaptic density, status of NSC in SVZ, and status of newborn neurons in olfactory bulb (OB) were assessed 6 months after stereotactic injection of oligomer Aß1-42 into the dens gyrus (DG) of hIAPP-/+ mice or wild-type homogenous mice. Our results set out that Aß42 and amylin co-localized into OB and raised Aß42 deposition in hIAPP-/+ mice compared with wild-type brood mice. In addition, 6 months after injection of Aß1-42 in hIAPP-/+ mice, these mice showed increased olfactory dysfunction, significant loss of synapses, depletion of NSC in SVZ, and impaired cell renewal in OB. Our present study suggested that the synergistic effects between hIAPP and Aß1-42 impairs olfactory function and was associated with decreased neurogenesis in adults with SVZ.

Site-Selective Photosynthesis of Ag-AgCl@Au Nanomushrooms for NIR-II Light-Driven O2- and O2•--Evolving Synergistic Photothermal Therapy against Deep Hypoxic Tumors.

Light-driven endogenous water oxidation has been considered as an attractive and desirable way to obtain O2 and reactive oxygen species (ROS) in the hypoxic tumor microenvironment. However, the use of a second near-infrared (NIR-II) light to achieve endogenous H2O oxidation to alleviate tumor hypoxia and realize deep hypoxic tumor phototherapy is still a challenge. Herein, novel plasmonic Ag-AgCl@Au core-shell nanomushrooms (NMs) were synthesized by the selective photodeposition of plasmonic Au at the bulge sites of the Ag-AgCl nanocubes (NCs) under visible light irradiation. Upon NIR-II light irradiation, the resulting Ag-AgCl@Au NMs could oxidize endogenous H2O to produce O2 to alleviate tumor hypoxia. Almost synchronously, O2 could react with electrons on the conduction band of the AgCl core to generate superoxide radicals (O2•-)for photodynamic therapy. Moreover, Ag-AgCl@Au NMs with an excellent photothermal performance could further promote the phototherapy effect. In vitro and in vivo experimental results show that the resulting Ag-AgCl@Au NMs could significantly improve tumor hypoxia and enhance phototherapy against a hypoxic tumor. The present study provides a new strategy to design H2O-activatable, O2- and ROS-evolving NIR II light-response nanoagents for the highly efficient and synergistic treatment of deep O2-deprived tumor tissue.

Interaction of human IAPP and Aß1-42 aggravated the AD-related pathology and impaired the cognition in mice.

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM) have a common pathology. Both diseases are characterized by local deposition of amyloid proteins in the brain or islet organ, but their phenotypes and clinical manifestation vary widely. Although the sources of islet amyloid polypeptide (IAPP) and amyloid beta (Aß) are independent, their fibrillar sequences are highly homologous. The prevalence of AD in T2DM populations is considerably higher than that in the normal population, but a mechanistic linkage remains elusive. Therefore, the present study aimed to explore the effects of Aß42 deposition in the brain on the persistently expression of human IAPP (hIAPP). Additionally, cognitive ability, synaptic plasticity, the state of neural stem cells and mitochondrial function were evaluated at 2 or 6 months after stereotaxically injected the oligomer Aß1-42 into the dentate gyrus of hIAPP (-/+) mice or the wild-type littermates. We found that Aß42 and amylin were co-located in hippocampus and Aß42 levels increased when Aß1-42 was injected in hIAPP transgenic mice compared with that of the wild-type littermates. Furthermore, at 6 months after Aß1-42 injection in hIAPP (-/+) mice, it exhibits exacerbated AD-related pathologies including Aß42 deposition, cognitive impairment, synapse reduction, neural stem cells exhaustion and mitochondrial dysfunction. Our present study suggested that hIAPP directly implicated the Aß42 production and deposition as an important linkage between T2DM and AD.

Noncanonical Roles of hα-syn (A53T) in the Pathogenesis of Parkinson's Disease: Synaptic Pathology and Neuronal Aging.

The motor and nonmotor symptoms of PD involve several brain regions. However, whether α-syn pathology originating from the SNc can directly lead to the pathological changes in distant cerebral regions and induce PD-related symptoms remains unclear. Here, AAV9-synapsin-mCherry-human SNCA (A53T) was injected into the unilateral SNc of mice. Motor function and olfactory sensitivity were evaluated. Our results showed that AAV9-synapsin-mCherry-human SNCA was continuously expressed in SNc. The animals showed mild motor and olfactory dysfunction at 7 months after viral injection. The pathology in SNc was characterized by the loss of dopaminergic neurons accompanied by ER stress. In the striatum, hα-syn expression was high, CaMKß-2 and NR2B expression decreased, and active synapses reduced. In the olfactory bulb, hα-syn expression was high, and aging cells in the mitral layer increased. The results suggested that hα-syn was transported in the striatum and OB along the nerve fibers that originated from the SNc and induced pathological changes in the distant cerebral regions, which contributed to the motor and nonmotor symptoms of PD.

Protective effect of metformin against rotenone-induced parkinsonism in mice.

Rotenone is a mitochondrial complex I inhibitor, which can cause the death of dopaminergic (DA) neurons and Parkinson's disease (PD). Currently, whether metformin has a protective effect on neurotoxicity induced by rotenone is unclear. The purpose of this study was to evaluate the potential protective effect of metformin against rotenone-induced neurotoxicity. PD animal model was established by unilateral rotenone injection into the right substantia nigra (SN) of C57BL/6 mice. The behavioral tests were performed by rotarod test and cylinder test. The numbers of TH-positive neurons and Iba-1 positive microglia in the SN were investigated by immunohistochemical staining. The mRNA levels of proinflammatory cytokines (TNF-α and IL-1ß) and molecules involved in endoplasmic reticulum (ER) stress (ATF4, ATF6, XBP1, Grp78, and CHOP) in the midbrain were detected by Quantitative real-time PCR. This study showed that 50 mg/kg metformin given orally daily, beginning 3 d before rotenone injection and continuing for 4 weeks following rotenone injection, significantly ameliorated dyskinesia, increased the number of TH-positive neurons, and mitigated the activation of microglia in the SN in rotenone-induced PD mice. Furthermore, 50 mg/kg metformin markedly downregulated the expression of proinflammatory cytokines (TNF-α and IL-1ß) and ER stress-related genes (ATF4, ATF6, XBP1, Grp78, and CHOP) in rotenone-induced PD mice. Metformin has a protective effect on DA neurons against rotenone-induced neurotoxicity through inhibiting neuroinflammation and ER stress in PD mouse model.

Fibrillation of human islet amyloid polypeptide and its toxicity to pancreatic ß-cells under lipid environment.

BACKGROUND: Previous studies suggested that fibrillar human IAPP (hIAPP) is more likely to deposit in ß-cells, resulting in ß-cell injury. However, the changes in the conformation of hIAPP in lipid environment and the mechanism involved in ß-cell damage are unclear. METHODS: Synthetic hIAPP was incubated with five types of free fatty acids and phospholipids 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS), which constitute the cell membrane. Thioflavin-T fluorescence assay was conducted to analyze the degree of hIAPP fibrosis, and circular dichroism spectroscopy was performed to detect the ß-fold formation of hIAPP. Furthermore, INS-1 cells were infected with human IAPP delivered by a GV230-EGFP plasmid. The effects of endogenous hIAPP overexpression induced by sodium palmitate on the survival, endoplasmic reticulum (ER) stress, and apoptosis of INS-1 cells were evaluated. RESULTS: The five types of free fatty acids can accelerate the fibrosis of hIAPP. Sodium palmitate also maintained the stability of fibrillar hIAPP. POPS, not POPC, accelerated hIAPP fibrosis. Treatment of INS-1 cells with sodium palmitate increased the expression of hIAPP, activated ER stress and ER stress-dependent apoptosis signaling pathways, and increased the apoptotic rate. CONCLUSION: Free fatty acids and anionic phospholipid can promote ß-fold formation and fibrosis in hIAPP. High lipid induced the overexpression of hIAPP and aggravated ER stress and apoptosis in INS-1 cells, which caused ß-cell death in high lipid environment. GENERAL SIGNIFICANCE: Our study reveals free fatty acids and hIAPP synergistically implicated in endoplasmic reticulum stress and apoptosis of islet ß-cells.

High-Fat Diet Increases Amylin Accumulation in the Hippocampus and Accelerates Brain Aging in hIAPP Transgenic Mice.

The accumulation of human islet amyloid polypeptide (hIAPP) in pancreatic islets under induction by a high-fat diet plays a critical role in the development of type-2 diabetes mellitus (T2DM). T2DM is a risk factor of late-onset Alzheimer's disease (AD). Nevertheless, whether hIAPP in combination with hyperlipidemia may lead to AD-like pathological changes in the brain remains unclear. hIAPP transgenic mice were fed with a high-fat diet for 6 or 12 months to establish the T2DM model. The accumulation of amylin, the numbers of Fluoro-Jade C (FJC)-positive and ß-gal positive cells, and the deposition level of Aß42 in the hippocampi of the transgenic mice were detected by using brain sections. Cytoplasmic and membrane proteins were extracted from the hippocampi of the transgenic mice, and the ratio of membrane GLUT4 expression to cytoplasmic GLUT4 expression was measured through Western blot analysis. Changes in the cognitive functions of hIAPP transgenic mice after 12 months of feeding with a high-fat diet were evaluated. hIAPP transgenic mice fed with a high-fat diet for 6 or 12 months showed elevated blood glucose levels and insulin resistance; increased amylin accumulation, number of FJC-positive and ß-gal positive cells, and Aß42 deposition in the hippocampi; and reduced membrane GLUT4 expression levels. hIAPP transgenic mice fed with a high-fat diet for 12 months showed reductions in social cognitive ability and passive learning ability. A high-fat diet increased amylin accumulation in the hippocampi of hIAPP transgenic mice, which presented AD-like pathology and behavior characterized by neural degeneration, brain aging, Aß42 deposition, and impaired glucose utilization and cognition.

Spermidine ameliorates the neuronal aging by improving the mitochondrial function in vitro.

Changes in mitochondrial structure and function are the initial factors of cell aging. Spermidine has an antiaging effect, but its effect on neuronal aging and mitochondrial mechanisms is unclear. In this study, mouse neuroblastoma (N2a) cells were treated with d­galactose (d­Gal) to establish cell aging to investigate the antiaging effect and mechanisms of spermidine. Changes in the cell cycle and ß-galactosidase activity were analyzed to evaluate the extent of cell aging. Stabilities of mitochondrial mRNA and mitochondrial membrane potential (MMP) were evaluated in the process of cell aging under different treatments. The mitochondrial function was also evaluated using the Seahorse Metabolic Analysis System combined with ATP production. The unfolded protein response (UPR) of the N2a cells was analyzed under different treatments. Results showed that spermidine pretreatment could delay the cell aging and could maintain the mitochondrial stability during d­Gal treatment. Spermidine increased the proportion of cells in the S phase and maintained the MMP. The oxygen utilization and ATP production in the N2a cells were reduced by d­Gal treatment but were partially rescued by the spermidine pretreatment. Spermidine ameliorated the N2a cell aging by promoting the autophagy and inhibiting the apoptosis except the UPR. These results showed that spermidine could ameliorate the N2a cell aging by maintaining the mitochondrial mRNA transcription, MMP and oxygen utilization during the d­Gal treatment.

Interaction of basolateral amygdala, ventral hippocampus and medial prefrontal cortex regulates the consolidation and extinction of social fear.

BACKGROUND: Following a social defeat, the balanced establishment and extinction of aversive information is a beneficial strategy for individual survival. Abnormal establishment or extinction is implicated in the development of mental disorders. This study investigated the time course of the establishment and extinction of aversive information from acute social defeat and the temporal responsiveness of the basolateral amygdala (BLA), ventral hippocampus (vHIP) and medial prefrontal cortex (mPFC) in this process. METHODS: Mouse models of acute social defeat were established by using the resident-intruder paradigm. To evaluate the engram of social defeat, the intruder mice were placed into the novel context at designated time to test the social behavior. Furthermore, responses of BLA, vHIP and mPFC were investigated by analyzing the expression of immediate early genes, such as zif268, arc, and c-fos. RESULTS: The results showed after an aggressive attack, aversive memory was maintained for approximately 7 days before gradually diminishing. The establishment and maintenance of aversive stimulation were consistently accompanied by BLA activity. By contrast, vHIP and mPFC response was inhibited from this process. Additionally, injecting muscimol (Mus), a GABA receptor agonist, into the BLA alleviated the freezing behavior and social fear and avoidance. Simultaneously, Mus treatment decreased the zif268 and arc expression in BLA, but it increased their expression in vHIP. CONCLUSION: Our data support and extend earlier findings that implicate BLA, vHIP and mPFC in social defeat. The time courses of the establishment and extinction of social defeat are particularly consistent with the contrasting BLA and vHIP responses involved in this process.

Lipid accelerating the fibril of islet amyloid polypeptide aggravated the pancreatic islet injury in vitro and in vivo.

BACKGROUND: The fibrillation of islet amyloid polypeptide (IAPP) triggered the amyloid deposition, then enhanced the loss of the pancreatic islet mass. However, it is not clear what factor is the determinant in development of the fibril formation. The aim of this study is to investigate the effects of lipid on IAPP fibril and its injury on pancreatic islet. METHODS: The fibril form of human IAPP (hIAPP) was tested using thioflavin-T fluorescence assay and transmission electron microscope technology after incubated with palmitate for 5 h at 25 °C. The cytotoxicity of fibril hIAPP was evaluated in INS-1 cells through analyzing the leakage of cell membrane and cell apoptosis. Type 2 diabetes mellitus (T2DM) animal model was induced with low dose streptozotocin combined the high-fat diet feeding for two months in rats. Plasma biochemistry parameters were measured before sacrificed. Pancreatic islet was isolated to evaluate their function. RESULTS: The results showed that co-incubation of hIAPP and palmitate induced more fibril form. Fibril hIAPP induced cell lesions including cell membrane leakage and cell apoptosis accompanied insulin mRNA decrease in INS-1 cell lines. In vivo, Plasma glucose, triglyceride, rIAPP and insulin increased in T2DM rats compared with the control group. In addition, IAPP and insulin mRNA increased in pancreatic islet of T2DM rats. Furthermore, T2DM induced the reduction of insulin receptor expression and cleaved caspase-3 overexpression in pancreatic islet. CONCLUSIONS: Results in vivo and in vitro suggested that lipid and IAPP plays a synergistic effect on pancreatic islet cell damage, which implicated in enhancing the IAPP expression and accelerating the fibril formation of IAPP.

Adult neural stem cell dysfunction in the subventricular zone of the lateral ventricle leads to diabetic olfactory defects.

Sensitive smell discrimination is based on structural plasticity of the olfactory bulb, which depends on migration and integration of newborn neurons from the subventricular zone. In this study, we examined the relationship between neural stem cell status in the subventricular zone and olfactory function in rats with diabetes mellitus. Streptozotocin was injected through the femoral vein to induce type 1 diabetes mellitus in Sprague-Dawley rats. Two months after injection, olfactory sensitivity was decreased in diabetic rats. Meanwhile, the number of BrdU-positive and BrdU+/DCX+ double-labeled cells was lower in the subventricular zone of diabetic rats compared with age-matched normal rats. Western blot results revealed downregulated expression of insulin receptor ß, phosphorylated glycogen synthase kinase 3ß, and ß-catenin in the subventricular zone of diabetic rats. Altogether, these results indicate that diabetes mellitus causes insulin deficiency, which negatively regulates glycogen synthase kinase 3ß and enhances ß-catenin degradation, with these changes inhibiting neural stem cell proliferation. Further, these signaling pathways affect proliferation and differentiation of neural stem cells in the subventricular zone. Dysfunction of subventricular zone neural stem cells causes a decline in olfactory bulb structural plasticity and impairs olfactory sensitivity in diabetic rats.

Role of Arcuate Nucleus in the Regulation of Feeding Behavior in the Process of Altitude Acclimatization in Rats.

Liu, Xiang-Wen, Jie Yin, Qi-Sheng Ma, Chu-Chu Qi, Ji-Ying Mu, Lang Zhang, Li-Ping Gao, and Yu-Hong Jing. Role of arcuate nucleus in the regulation of feeding behavior in the process of altitude acclimatization in rats. High Alt Med Biol. 18:234-241, 2017.-Highly efficient energy utilization and metabolic homeostasis maintenance rely on neuromodulation. Altitude exposure is known to stimulate neuroendocrine systems to respond to acute hypoxia and adaptive acclimatization. However, limited data on how the adaptive regulation of the arcuate nucleus performs in the process of altitude acclimatization are available. In the present study, male Sprague Dawley rats were transported to Huashixia, Qinghai (with an altitude of 4400 m) from Xian (with an altitude of 300 m) by air; rats were consistently raised in Xian as control. Food uptake and body weight were measured consecutively after being subjected to high-altitude condition. Contents of plasma leptin and ghrelin were analyzed by the Enzyme Linked Immunosorbent Assay (ELISA) Kits. Brain coronal sections were obtained, and neuropeptide Y (NPY), proopiomelanocotin (POMC), and c-fos immunoreactivity in arcuate nucleus were observed. Arcuate nucleus was isolated from the hypothalamus, and the mRNA of NPY and POMC were measured by quantitative real-time polymerase chain reaction. Our results showed both food consumption and body weight decreased in the high plateau compared with rats raised in the low-altitude condition. Plasma leptin increased at the early stage, and ghrelin decreased at a later stage after reaching the high plateau. The peak of c-fos immunoreactivity in the arcuate nucleus was at day 3 after reaching the high plateau. The expression level of NPY increased, and POMC decreased in the arcuate nucleus at day 7 after reaching the high plateau compared with the plain control group. These results indicate that the arcuate nucleus of hypothalamus performs an important function in regulating feeding behavior during altitude acclimatization. Our study suggested that altitude acclimation is regulated by the hypothalamus that received leptin and ghrelin signals to response by its microcircuit, including NPY- and POMC-neurons in the arcuate nucleus.

Autophagy plays beneficial effect on diabetic encephalopathy in type 2 diabetes: studies in vivo and in vitro.

OBJECTIVES: The hypothalamus regulates metabolism and feeding behavior by perceiving the levels of peripheral insulin. However, little is known about the hypothalamic changes after aberrant metabolism. In this study, we investigated the changes of insulin and autophagy relevant signals of hypothalamus under diabetes mellitus. METHODS: C57B/L mice were injected with low-dose streptozotocin (STZ) and fed with high-fat diet to induce type 2 diabetes mellitus. In vitro, PC12 cells were treated with oleic acid to mimic lipotoxicity. RESULTS: Results showed that the cholesterol level in the hypothalamus of the diabetic mice was higher than that of the normal mice. The expression of insulin receptors and insulin receptor substrate-1 were downregulated and the number of Fluoro-Jade C positive cells significantly increased in the hypothalamic arcuate nucleus of the diabetic mice. Furthermore, Upregulation of mammalian target of rapamycin (mTOR) and downregulation of LC 3II were obvious in the hypothalamus of the diabetic mice. In vitro, results showed that high-lipid caused PC12 cell damage and upregulated LC3 II expression. Pretreatment of cells with 3-methyladenine evidently downregulated LC3 II expression and aggravated PC12 cell death under high lipid conditions. By contrast, pretreatment of cells with rapamycin upregulated LC3 II expression and ameliorated PC12 cell death caused by lipotoxicity. CONCLUSION: These results demonstrate that autophagy activation confers protection to neurons under aberrant metabolism and that autophagy dysfunction in the hypothalamus occurs in the chronic metabolic disorder such as T2DM.

Spermidine preconditioning ameliorates laurate-induced brain injury by maintaining mitochondrial stability.

Ischemic precondition plays a protective effect during cerebral ischemia. This effect partly depends on the autophagic activity. However, whether the activity of autophagy can exert the protective effects after cerebral ischemia is unclear. In this study, rats were treated with spermidine, an activator of autophagy, and injected with sodium laurate via the internal carotid artery to stimulate cerebral small vessel disease (CSVD). The effects of the spermidine precondition on brain injury were evaluated by behavioural test, histology assay, ultrastructure observation, and autophagic-related signals. Furthermore, the mitochondria of brain tissue were isolated, and mitDNA were extracted. The stability of mitDNA was analyzed by quantitative real-time PCR. Results showed that the penetrating artery of the striatum was damaged. This damage was accompanied by neural inflammation characterized by an increase in Fluoro-Jade C (FJC)-positive cells after sodium laurate injection. Spermidine pretreatment decreased the deletion of mitDNA and the autophagy hyperactivity induced by the laurate injection. Likewise, spermidine reduced the neurological deficit and FJC reactivation of striatum at 48 h after laurate injection. These results suggested sodium laurate injection through the internal carotid artery can induce the pathological features of CSVD characterized by the damage of penetrating artery, neurological deficit, mitochondrial impairment, and autophagic hyperactivity. Pretreatment with spermidine can ameliorate these outcomes. Further study indicated that the protective effect of the spermidine precondition is associated with the maintenance of mitochondrial stability and proper autophagy activity.